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<FONT color="green">001</FONT>    /*<a name="line.1"></a>
<FONT color="green">002</FONT>     * Licensed to the Apache Software Foundation (ASF) under one or more<a name="line.2"></a>
<FONT color="green">003</FONT>     * contributor license agreements.  See the NOTICE file distributed with<a name="line.3"></a>
<FONT color="green">004</FONT>     * this work for additional information regarding copyright ownership.<a name="line.4"></a>
<FONT color="green">005</FONT>     * The ASF licenses this file to You under the Apache License, Version 2.0<a name="line.5"></a>
<FONT color="green">006</FONT>     * (the "License"); you may not use this file except in compliance with<a name="line.6"></a>
<FONT color="green">007</FONT>     * the License.  You may obtain a copy of the License at<a name="line.7"></a>
<FONT color="green">008</FONT>     *<a name="line.8"></a>
<FONT color="green">009</FONT>     *     http://www.apache.org/licenses/LICENSE-2.0<a name="line.9"></a>
<FONT color="green">010</FONT>     *<a name="line.10"></a>
<FONT color="green">011</FONT>     * Unless required by applicable law or agreed to in writing, software<a name="line.11"></a>
<FONT color="green">012</FONT>     * distributed under the License is distributed on an "AS IS" BASIS,<a name="line.12"></a>
<FONT color="green">013</FONT>     * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.<a name="line.13"></a>
<FONT color="green">014</FONT>     * See the License for the specific language governing permissions and<a name="line.14"></a>
<FONT color="green">015</FONT>     * limitations under the License.<a name="line.15"></a>
<FONT color="green">016</FONT>     */<a name="line.16"></a>
<FONT color="green">017</FONT>    package org.apache.commons.configuration.tree;<a name="line.17"></a>
<FONT color="green">018</FONT>    <a name="line.18"></a>
<FONT color="green">019</FONT>    import java.util.List;<a name="line.19"></a>
<FONT color="green">020</FONT>    <a name="line.20"></a>
<FONT color="green">021</FONT>    /**<a name="line.21"></a>
<FONT color="green">022</FONT>     * &lt;p&gt;<a name="line.22"></a>
<FONT color="green">023</FONT>     * Definition of an interface for evaluating keys for hierarchical<a name="line.23"></a>
<FONT color="green">024</FONT>     * configurations.<a name="line.24"></a>
<FONT color="green">025</FONT>     * &lt;/p&gt;<a name="line.25"></a>
<FONT color="green">026</FONT>     * &lt;p&gt;<a name="line.26"></a>
<FONT color="green">027</FONT>     * An &lt;em&gt;expression engine&lt;/em&gt; knows how to map a key for a configuration's<a name="line.27"></a>
<FONT color="green">028</FONT>     * property to a single or a set of configuration nodes. Thus it defines the way<a name="line.28"></a>
<FONT color="green">029</FONT>     * how properties are addressed in this configuration. Methods of a<a name="line.29"></a>
<FONT color="green">030</FONT>     * configuration that have to handle property key (e.g.<a name="line.30"></a>
<FONT color="green">031</FONT>     * {@code getProperty()} or {@code addProperty()} do not interpret<a name="line.31"></a>
<FONT color="green">032</FONT>     * the passed in keys on their own, but delegate this task to an associated<a name="line.32"></a>
<FONT color="green">033</FONT>     * expression engine. This expression engine will then find out, which<a name="line.33"></a>
<FONT color="green">034</FONT>     * configuration nodes are addressed by the key.<a name="line.34"></a>
<FONT color="green">035</FONT>     * &lt;/p&gt;<a name="line.35"></a>
<FONT color="green">036</FONT>     * &lt;p&gt;<a name="line.36"></a>
<FONT color="green">037</FONT>     * Separating the task of evaluating property keys from the configuration object<a name="line.37"></a>
<FONT color="green">038</FONT>     * has the advantage that many different expression languages (i.e. ways for<a name="line.38"></a>
<FONT color="green">039</FONT>     * querying or setting properties) can be supported. Just set a suitable<a name="line.39"></a>
<FONT color="green">040</FONT>     * implementation of this interface as the configuration's expression engine,<a name="line.40"></a>
<FONT color="green">041</FONT>     * and you can use the syntax provided by this implementation.<a name="line.41"></a>
<FONT color="green">042</FONT>     * &lt;/p&gt;<a name="line.42"></a>
<FONT color="green">043</FONT>     *<a name="line.43"></a>
<FONT color="green">044</FONT>     * @since 1.3<a name="line.44"></a>
<FONT color="green">045</FONT>     * @author &lt;a<a name="line.45"></a>
<FONT color="green">046</FONT>     * href="http://commons.apache.org/configuration/team-list.html"&gt;Commons<a name="line.46"></a>
<FONT color="green">047</FONT>     * Configuration team&lt;/a&gt;<a name="line.47"></a>
<FONT color="green">048</FONT>     * @version $Id: ExpressionEngine.java 1206474 2011-11-26 16:14:09Z oheger $<a name="line.48"></a>
<FONT color="green">049</FONT>     */<a name="line.49"></a>
<FONT color="green">050</FONT>    public interface ExpressionEngine<a name="line.50"></a>
<FONT color="green">051</FONT>    {<a name="line.51"></a>
<FONT color="green">052</FONT>        /**<a name="line.52"></a>
<FONT color="green">053</FONT>         * Finds the node(s) that is (are) matched by the specified key. This is the<a name="line.53"></a>
<FONT color="green">054</FONT>         * main method for interpreting property keys. An implementation must<a name="line.54"></a>
<FONT color="green">055</FONT>         * traverse the given root node and its children to find all nodes that are<a name="line.55"></a>
<FONT color="green">056</FONT>         * matched by the given key. If the key is not correct in the syntax<a name="line.56"></a>
<FONT color="green">057</FONT>         * provided by that implementation, it is free to throw a (runtime)<a name="line.57"></a>
<FONT color="green">058</FONT>         * exception indicating this error condition.<a name="line.58"></a>
<FONT color="green">059</FONT>         *<a name="line.59"></a>
<FONT color="green">060</FONT>         * @param root the root node of a hierarchy of configuration nodes<a name="line.60"></a>
<FONT color="green">061</FONT>         * @param key the key to be evaluated<a name="line.61"></a>
<FONT color="green">062</FONT>         * @return a list with the nodes that are matched by the key (should never<a name="line.62"></a>
<FONT color="green">063</FONT>         * be &lt;b&gt;null&lt;/b&gt;)<a name="line.63"></a>
<FONT color="green">064</FONT>         */<a name="line.64"></a>
<FONT color="green">065</FONT>        List&lt;ConfigurationNode&gt; query(ConfigurationNode root, String key);<a name="line.65"></a>
<FONT color="green">066</FONT>    <a name="line.66"></a>
<FONT color="green">067</FONT>        /**<a name="line.67"></a>
<FONT color="green">068</FONT>         * Returns the key for the specified node in the expression language<a name="line.68"></a>
<FONT color="green">069</FONT>         * supported by an implementation. This method is called whenever a property<a name="line.69"></a>
<FONT color="green">070</FONT>         * key for a node has to be constructed, e.g. by the<a name="line.70"></a>
<FONT color="green">071</FONT>         * {@link org.apache.commons.configuration.Configuration#getKeys() getKeys()}<a name="line.71"></a>
<FONT color="green">072</FONT>         * method.<a name="line.72"></a>
<FONT color="green">073</FONT>         *<a name="line.73"></a>
<FONT color="green">074</FONT>         * @param node the node, for which the key must be constructed<a name="line.74"></a>
<FONT color="green">075</FONT>         * @param parentKey the key of this node's parent (can be &lt;b&gt;null&lt;/b&gt; for<a name="line.75"></a>
<FONT color="green">076</FONT>         * the root node)<a name="line.76"></a>
<FONT color="green">077</FONT>         * @return this node's key<a name="line.77"></a>
<FONT color="green">078</FONT>         */<a name="line.78"></a>
<FONT color="green">079</FONT>        String nodeKey(ConfigurationNode node, String parentKey);<a name="line.79"></a>
<FONT color="green">080</FONT>    <a name="line.80"></a>
<FONT color="green">081</FONT>        /**<a name="line.81"></a>
<FONT color="green">082</FONT>         * Returns information needed for an add operation. This method gets called<a name="line.82"></a>
<FONT color="green">083</FONT>         * when new properties are to be added to a configuration. An implementation<a name="line.83"></a>
<FONT color="green">084</FONT>         * has to interpret the specified key, find the parent node for the new<a name="line.84"></a>
<FONT color="green">085</FONT>         * elements, and provide all information about new nodes to be added.<a name="line.85"></a>
<FONT color="green">086</FONT>         *<a name="line.86"></a>
<FONT color="green">087</FONT>         * @param root the root node<a name="line.87"></a>
<FONT color="green">088</FONT>         * @param key the key for the new property<a name="line.88"></a>
<FONT color="green">089</FONT>         * @return an object with all information needed for the add operation<a name="line.89"></a>
<FONT color="green">090</FONT>         */<a name="line.90"></a>
<FONT color="green">091</FONT>        NodeAddData prepareAdd(ConfigurationNode root, String key);<a name="line.91"></a>
<FONT color="green">092</FONT>    }<a name="line.92"></a>




























































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